Speedometer.



G. S. TWFNY.,

SPEEDOWIETER.

APPLICATION men ocr. 24. 1914.

Mmmm Aug., 29, 119%?.

l ill ci GEORGE S. TIFFANY, OF SUMMIT, NEW JERSEY, ASSIGNOR T THE DEVICETESTING COMPANY, A CORPCRATION OF CONNECTICUT.

SPEEDOMETER.

Specification of Letters Patent.

Patented Aue. 29, 1916.

Application led October 2t, 1914. Serial No. 868,364.

To IZ whom it may concern:

lie. it known that I, GEORGE S. TIFFANY, a citizen of the United Statesof America, and a resident of Summit, Union county, New Jersey, haveinvented certain new `and useful 'Improvements in Speedometers, of whichthe following is a specification. f

'l his invention relates to improvements in electrically operatedmechanisms or apparatus, such as speedometers for instance, yand theobject of the invention is to provide cer` tain improvements incombination with the speedometer or other apparatus whereby to simplifythe operation thereof and to eliminate certain disturbing infiuences orfactors with a view of rendering the speedometer or other apparatusdependable and certain in its functions and operations.

lith this and other objects in view, all

of which will be pointed out as this speciication proceeds, theinvention is embodied in and comprises the elements arranged andcombined with a speedometer as hereinafter set forth and as shown in theaccompanying drawing which illustrates an electrically operatedspeedometer improved according to my invention and in which drawing-Figure 1 isa wiring diagram illustrating the invention. Fig. 2 is adetail view of the eonimutator. -Fig. 3 is a plan view of thespeedometer. and Fig. 4 is a substantially central sectional view of thespeedometer.

.fait

The speedometer as herein described and illustrated comprises anelectromagnet wound to provide a rotating magnetic field having acentrally disposed non-rotatable armature between which and theelectromagnetthere is mounted a movable indicating element in inductiverelation to the magnet. Suitable means are provided for supplyingcurrent to the electromagnet.

Referring to the drawing the numeral indicates the armature of soft ironlaminas suitably mounted within a casing 11 of non magnetic material.Surrounding the armature 10 there is provided an electromagnetcomprising the core 1Q and the poles 13 between whiclry are wound thecoils 14. The latter are connected serially to the segments 15 of acommutator 1G which is suitably secured' to a bracket 17 which may forma bearing for the shaft 18the speed of which is to be measured.

19, 19 are brushes mounted in a brush holder 20 which is secured so asto rotate with the shaft 18. The brushes are connected across thebattery 21, or other source of electrical energy by the battery circuitQQ, QQ in which 23 represents a controlling switch. Current is suppliedto the brushes 1*.) by way of sliding contacts Q4 in an obvious manner.

From this description it is apparent that during the rotation of theshaft 18 a rotating magnetic eld is produced between the armature andthe eleetromagnet.

The speed indicator 25 of aluminum or similar material is mounted torotate betweenthe armature and the eleetromagnet 12-14 so as to cut themagnetic lines of force between these two elements. For this purpose theindicator is provided with a skirt or cylinder QG which surrounds thearmature as shown. The indicator is provided with a scale Q7 which isread with reference to a fixed mark QS on the cover of the casing 11.-The pivot 29 of the indicator has its bearings `in the cover and in thearmature as shown.

30 is a hair spring which tends to keep the indicator at zero positionand 31 represents stops for liniiting'the movement of the indicator.

The rotating magnetic field produced when the shaft 18 is rotated andthe battery circuit is closed imparts a rotative tendency to theindicator in the direction of rotation of the magnetic field and indirect propor tion to the rotative speed of the shaft, such rotativetendency being opposed by the spring 30 in such a proportion withrespect to the magnetic effect created by the electromagnet as to causethe indicator to re- .volve to an extent 1n direct proportion to thespeed of the shaft 18, and hence when said indicator is properlycalibrated, the exact speed of the-rotation of the shaft will beindicated in the graduations of the scale 97 with referenceto the mark28. The stops 31 prevent the indicator from making more than onerevolution as will be understood'.

From the foregoing it will be clear that the speed of the shaft 18 maybe read directly by means of the scale 2.7 in the indieator because themovement of the latter is in direct proportion to the speed of theshaft. This condition.y however, exists only while the strength of therotating ma etic field remains practically constant. qliiriationtherein, which is due to variations in the voltage `of the current,influences the nuwcment of the indicator as is obvious and thc latterdoes not then correctly indicate the speed of the operating shaft 18. Aninances caused by variations in the strengthv of the rotating magneticfield due to an increase or decrease in voltage in the circuit from thatfor which the apparatus is designed. To this end there is inserted inthe battery circuit 22, 22 an electromagnet 32 having a pivoted armature33 which is kept in contact with a contact 34 by means of a spring 35.AA resistance 36 is connected between the arn'iature 33 and the circuit2Q. The spring and the eleetroxnagnet 3Q`are so proportioned that whenthe voltage in the circuit is normal or equal to that for which theapparatus is designed, the electromagnet is not strong enough toovercome the force of the spring. The contact of the armature at 3lremains closed. and the operating circuit is traced through theclcctromagnet 32, the armature 33, the contact 34 and through the wires9:2 to the speedometer. At a higher voltage, the electromagnet 32overcomes the resistance of the spring 35 and attracts .the armature 33Which puts the resistance 36 in the circuit so that the voltage for thespeedometer is not increased.

When the battery is the sole source of.

current sup ly it is preferably overcharged so that it will dischargecurrent at a higher to charge the latter in which case the resistancewill be put into or cut out of the circuit automatically and in responseto variationsin the voltage, but will not neces- `sarily be in thecircuit at the start of the operation of the speedometer.

41 represents diagrammatically a speed controller switch and i2 areversel relay such as are usual and well known in the art for theproper operation of the generator.

Thus it will be seen, that whether thc circuit commences to operate at atoo high voltage for the speedometer or at normal or required voltagewhich thereafter varies, the voltage for the speedometer isautomatically regulated to that required for its proper operation.

From the foregoing it will bc seen that means have been provided wherebythe operation of the speedometer is automatically regulated with respectto variations in voltage andv that the disturbing influence of thelatter is eliminated.

While I have described the invention with reference to a specific formof speedometer and embodied the lprinciples of the invention in certainspecific elements, I do not wish to he understood as limiting myinvention to the embodiment illustrated and described, but claim allsuch modifications which properly come within the scope of the appendedclaim.

I claim The combination of a speed indicator, a shaft, electric meansfor operating said indicator kand controlled by the speed of said shaft,said electrioineans including a circuit, mechanism for compensatingchanges of voltage in said electric circuit and comprising anelectromagnet and arn'iature'connected in said circuit and a resistanceconnected to the latter and the said armature.

Signed at New York, N. Y., this 23d day of Oct., 1914.

GEORGE S. TIFFAN Y.

K. G. LE Ann.

